The floor of an automobile is typically covered by a floor mat, and an insulator in the form of an insulator board is interposed between the surface of a floor panel and the floor mat. Such a floor mat and insulator are typically secured to the floor panel by using a fastener such as the one shown in FIG. 6.
Referring to FIG. 6, after a female member 2 is fitted into a mounting hole la provided in a floor panel 1 to secure an insulator 3 onto the floor panel 1 therewith, a male member 4 securing a floor mat 5 is fitted into the female member 2 so that the insulator 3 and the floor mat 5 may be secured onto the floor panel 1 in a layered arrangement. The female member 2 is provided with a cup-shaped stem portion 16 which is to be fitted into an opening 3a of the insulator 3 and the mounting hole 1a, and a radial flange portion 17 extending outwardly from a base end of the stem portion 16, and the stem portion 16 is further provided with a pair of elastic engagement pieces 18 for preventing the female member 2 from coming off from the floor panel 1 by engaging with a lower surface of the floor panel 1 when the stem portion 16 is pushed into the mounting hole 1a.
The male member 4 is provided with a stem portion 13 which can be received inside the stem portion 16 of the female member 2, a pair of elastic legs 14 extending from a free end of the stem portion 13 in the opposite direction from the direction of fitting the stem portion 13 into the female member 2 and diverging in a symmetric fashion, and a disk-shaped head 11 extending radially from a base end of the stem portion 13. The stem portion 13 is further provided with a radial flange portion 12 which is spaced from the head 11 in a coaxial and parallel relationship. This flange portion 12 is divided into two semi-circular parts so that the floor mat 5 may be interposed between the head 11 and the flange portion 12 by passing the stem portion 13 through an opening 5a of the floor mat 5 and twisting each of the semi-circular parts of the flange portion 12 through the opening 5a.
According to this fastener, first of all, the stem portion 16 of the female member 2 is passed through the opening 3a of the insulator 3, and then through the mounting hole 1a with the insulator secured to the female member 2 until the elastic engagement pieces 18 are engaged by the lower surface of the floor panel 1 and the female member 2 is firmly secured to the floor panel 1. Then, the male member 4 with the floor mat 5 secured thereto as described above is coupled to the female member 2 by passing the stem portion 13 of the male member 4 into the interior of the female member 2 causing the teeth 14a provided in the elastic legs 14 to be pressed against the internal thread 16a provided in the female member 2 and the elastic legs 14 to be thereby elastically deformed, with the result that the insulator 3 and the floor mat 5 are secured to the floor panel 1 in a layered arrangement. The removal of the male member 4 can be readily accomplished by placing a tool into a groove provided in the head 11, and turning it in the direction to loosen the threading between the teeth 14a of the legs 14 and the internal thread 16a of the female member 2.
According to this conventional structure, the stem portion 16 of the female member 2 can move within the opening 3a of the insulator 3 in both the radial and axial directions when mounting the insulator 3 on the floor panel 1. Therefore, the female member 2 needs to be properly positioned with respect to the mounting hole 1a while aligning the opening 3a of the insulator 3 with the mounting hole 1a, and this complicates the process of positioning the various parts during the assembly work, thereby lowering the work efficiency.